Power Mac G4 Cube Troubleshooting
These are Apple's troubleshooting procedures and symptom charts for the Power Mac G4 Cube, from the Troubleshooting chapter of its Service Source.[1] Apple lists cures in order of likelihood; refit the original module before trying the next cure (p. 110). Removing the core and the modules named below is covered on Power Mac G4 Cube General Maintenance.
Apple notes that the only way to cut power completely is to unplug the computer and display, so keep their plugs within reach (p. 110).[1]
PMU reset
[edit | edit source]Do this before replacing anything in a Cube that will not power up (pp. 103–104):[1]
- Disconnect the power adapter. Check the battery reads 3.3 to 3.7 V; if not, replace it and wait ten seconds.
- With the video riser card and its J4 connector in place, press S1 on the logic board once. It is under the video card, near the edge at the end away from the video ports. Do not press it a second time.
- Wait ten seconds, reconnect the adapter and switch on. If the Cube still does not start, the fault is elsewhere.
- Run Apple Hardware Test, then set the date and time, which the reset clears.
Power adapter verification
[edit | edit source]The logic board needs a 28 V "trickle" from the external adapter to power on. After a PMU reset (pp. 105–106):[1]
- Make sure all cards and cables inside are seated, and that the adapter is on a known-good outlet and mains cord.
- Plug the adapter into the Cube and check that the green LED on the DC-to-DC board is lit.
- For a full check, measure J3 on the video riser card from the back of the card, with the cable still plugged in at J3 and at J11 on the logic board. It should read 28 V (+0.5 V, −1 V).
If the reading is missing, Apple replaces the power adapter (p. 110).
Power-on self test
[edit | edit source]The ROM test runs after a full shutdown. If it finds a fault there is no start-up sound, and the power light flashes; a flash here means a quarter of a second or longer (pp. 107–109):[1]
| Flashes | Meaning | Apple's cure |
|---|---|---|
| 2 | No memory installed or detected | Reseat the DIMMs, or fit compatible memory if none is installed; if the light still flashes, contact Apple |
| 3 | Incompatible memory types (for example SDRAM and EDO together) | Fit compatible PC100 memory |
| 4 | No memory bank passed the test | Remove all memory and check the slots for bent pins; if none, take out the video card, refit the video riser, wait ten seconds and press S1 once; refit the memory and test; then replace the DIMMs |
Start-up and power
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| No apparent power: no sound, power light off | Check the outlet; replace the power cord; reset the PMU; check the 28 V trickle and replace the adapter if it fails; disconnect external devices including the monitor; remove internal cards; disconnect the internal hard drive; reseat the DC-to-DC board; check the modem connector for bent pins (replace the logic board if any); replace the logic board |
| Power button lights when touched but goes out on release; Cube does not start | The DC-to-DC board may have moved slightly in its connector during shipping. Reseat it |
| Power light flashes in sequence | See the power-on self test above |
| Turns off or sleeps at random, or turns on or wakes at random | Put the Cube on a sturdy, flat surface with nothing on top; check Energy Saver settings; check the adapter and mains cord are firmly plugged in; remove and refit the DC-to-DC board; then go by the serial number (below) |
| Flashing question mark | Start from the Software Restore disc. If the drive appears, update its driver, run Disk First Aid, remove extra System Folders, clean-install, or back up and reinitialise. If not, reset PRAM and check the drive's cables. If the drive does not spin, measure J2 on the DC-to-DC board with only the adapter connected: pin 1 about 5 V, pin 4 about 12 V, pins 2 and 3 ground. Wrong voltages mean a new DC-to-DC board; correct ones mean a new hard drive |
Source: pp. 110–112.[1]
Random power-on, power-off, sleep or wake by serial number
[edit | edit source]Read the serial number on the base by the latch. Its format is PPYWWxxxxxx: plant, year (0 = 2000), week of manufacture, then the unit number. Apple's steps (pp. 112–113):[1]
- Year and week 035 or earlier (for example SG035MW6JDZ): go on to the next check.
- 036 to 039: replace the power button gasket, a customer-installable part.
- 040 or later: go on to the next check.
- Take off the top plate and look at the proximity switch plate screwed to the power button board under it. If the plate has a notch, or tape under it, go to the last step. If not, remove its two Torx screws, run a strip of Kapton tape 32 mm by 3 mm near the rounded edge of the power button board, refit the plate pressed against the flat edge of the board, and tighten the screws half way first, keeping light pressure so the plate stays level end to end.
- Check the underside of the top plate for the EMI gasket. If the plate is marked 805-2807, replace the top plate or the EMI gasket.
When fitting a new enclosure shell, the power button gasket must be level and centred, or the Cube may not power up (p. 22).[1]
Sound, video and memory
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Speakers go silent and USB devices stop responding, with an Apple Studio Display or Cinema Display (ADC) connected and music playing at full volume | Connect the speakers to the Cube instead of the display; restart and lower the volume. If the mouse does not respond, use the reset button on the bottom of the Cube |
| An ADC display shows no picture, though a VGA monitor works | Try a known-good ADC display with a known-good power source; check the display cable at the video card; reseat the video riser and video card; make sure the cable at J3 on the video riser card, which carries the ADC voltage, is pushed fully home |
| Memory error message | Reseat the DIMMs; check only PC-100 SDRAM is fitted; run Apple Hardware Test to find a bad DIMM and replace it. Apple's related article is titled "Power Mac G4 Cube: Must Use 35 mm RAM DIMMs" |
| "Apple DVD Player can not open because the required hardware was not found" | Quit other applications and reopen it; restart; start with the Mac OS 9 All extension set; clean-install the system; check the DVD-ROM drive's connections; replace the drive |
Source: pp. 114–115, 118.[1]
Modem and USB
[edit | edit source]Apple's modem charts deal mainly with software, scripts and phone lines; the hardware cures are to reseat and then replace the modem board (pp. 115–117). For a dead keyboard or mouse, check it is on a USB port, remove other USB devices, test with extensions off and from the Software Restore disc, try the mouse on a port on the Cube instead of the keyboard, and replace the keyboard or mouse (pp. 118–119).[1]
Related pages
[edit | edit source]- Power Mac G4 Cube
- Power Mac G4 Cube General Maintenance
- Power Mac G4 Cube Service Source
- Power Mac G4 Troubleshooting